基于SINBAD聚变基准题的cosRMC程序屏蔽计算研究

Shielding calculation based on SINBAD fusion benchmarks using cosRMC

聚变堆具有中子能量高、空间尺度大、几何结构复杂、辐射衰减梯度大等特点,其屏蔽计算更具挑战。为了验证蒙卡程序cosRMC在针对聚变堆屏蔽问题的准确性,对国际屏蔽基准题库SINBAD中的两个屏蔽实验进行了模拟。首先基于基准题实验模型建立了详细的三维中子学模型,通过cosRMC中子-光子耦合输运计算,对实验时在模型中处于不同中子穿透深度位置的探测器的中子能谱进行模拟计算。然后采用栅元重要性减方差技术进一步提高cosRMC屏蔽计算的精度。最后将cosRMC计算得到的中子通量谱与MCNP5的计算结果以及基准题实验值进行了对比。结果表明,cosRMC与MCNP5的计算结果相符,二者的相对误差在3倍相对统计误差以内,且与实验值吻合良好,证明了cosRMC具有进行聚变堆屏蔽计算的能力。

[Background]Fusion reactors have the characteristics of high neutron energy,large spatial scales,complex geometric structures,and large radiation attenuation gradients,which make nuclear design and analysis more challenging.[Purpose]This study aims to verify the accuracy of the calculation of Monte Carlo code cosRMC on the material shielding effect in fusion reactor applications.[Methods]Two deep penetration benchmarks,i.e.,FNS-Duct(Fusion Neutron Source Dogleg Duct Streaming)and FNS-W(FNS Clean Experiment on Tungsten Cylindrical Assembly)from the Shielding Integral Benchmark Archive Database(SINBAD),were taken for simulation study of the penetration behaviors of neutrons in models under different geometric shapes and materials.First of all,detailed cosRMC models was established based on benchmark experimental models,neutron flux spectra of detectors at different penetration depths in benchmark experiments were calculated using cosRMC.Then,the variance reduction technique of cell importance was applied to improving the accuracy of cosRMC in calculating deep penetration problems.Finally,neutron flux spectra calculated by cosRMC were compared with those calculated by MCNP5,as well as the experimental results of the benchmarks.[Results]The comparison results show that the calculations of cosRMC conform to that of MCNP5 with relative deviations of less than three times the standard errors.Both calculation results match well with the experimental values.[Conclusions]The study verifies that cosRMC can be applied to shielding calculations of fusion reactors.